Pop Airplay (also called Mainstream Top 40, Pop Songs, and Top 40/CHR) is a 40-song music chart published weekly by Billboard Magazine that ranks the most popular songs of pop music being played on a panel of Top 40 radio stations in the United States. The rankings are based on radio airplay detections as measured by Nielsen Broadcast Data Systems (Nielsen BDS), a subsidiary of the U.S.' leading marketing research company. Consumer researchers, Nielsen Audio (formerly Arbitron), refers to the format as contemporary hit radio (CHR). The current number-one song on the chart is "Lose Control" by Teddy Swims.^[1]

The chart debuted in Billboard Magazine in its issued date October 3, 1992, with the introduction of two Top 40 airplay charts, Mainstream and Rhythm-Crossover. Both Top 40 charts measured "actual monitored airplay" from data compiled by Broadcast Data Systems (BDS). The Top 40/Mainstream chart was compiled from airplay on radio stations playing a wide variety of music, while the Top 40/Rhythm-Crossover chart was made up from airplay on stations playing more dance and R&B music.^[2] Both charts were "born of then-new BDS electronic monitoring technology" as a more objective and precise way of measuring airplay on radio stations. This data was also used as the airplay component for Hot 100 tabulations.^[2] American Top 40 with Shadoe Stevens used this chart for their show from January 1993 to January 1995.

Top 40/Mainstream was published in the print edition of Billboard from its debut in October 1992 through May 1995, when both Top 40 charts were moved exclusively to Airplay Monitor, a secondary chart publication by Billboard. They returned to the print edition in the August 2, 2003, issue.^[3] The first number-one song on the chart was "End of the Road" by Boyz II Men.^[4]

There are forty positions on this chart. Songs are ranked based on its total number of spins per week. This is calculated by electronically monitoring Mainstream Top 40 radio stations across the U.S. 24 hours a day, seven days a week by Nielsen Broadcast Data Systems.

Songs receiving the greatest growth receive a "bullet", although there are tracks that also get bullets if the loss in detections doesn't exceed the percentage of downtime from a monitored station. "Airpower" awards are issued to songs that appear on the top 20 of both the airplay and audience chart for the first time, while the "greatest gainer" award is given to song with the largest increase in detections. A song with six or more spins in its first week is awarded an "airplay add". If two songs are tied in spins in the same week, the one with the biggest increase that week ranks higher.

Since the introduction of the chart until 2005, songs below No. 20 were moved to recurrent after 26 weeks on the chart. Beginning the chart week of December 3, 2005, songs below No. 20 were moved to recurrent after 20 weeks on the chart. Since the chart dated December 4, 2010, songs below No. 15 are moved to recurrent after 20 weeks on the chart

Whereas the Pop Airplay and Pop 100 Airplay charts both measured the airplay of songs played on Mainstream stations playing pop-oriented music, the Pop 100 Airplay (like the Hot 100 Airplay) measured airplay based on statistical impressions, while the Top 40 Mainstream chart used the number of total detections.

Source:^[5]

In 2012, for the 20th anniversary of the chart, Billboard compiled a ranking of the 100 best-performing songs on the chart over the 20 years, along with the best-performing artists. "Iris" by Goo Goo Dolls ranked as the #1 song on that list.^[6][7] In 2017, Billboard revised the rankings, including the methodologies for how they are calculated. "Another Night" by Real McCoy was the new #1 song, while the previous #1 song, "Iris", dropped to #8. Rihanna ranked as the top artist on both all-time charts.^[8] Shown below are the top 10 songs and the top 10 artists from the most recent chart.